Permissions

IC:
General friendly contact (handshakes, hugging, non-romantic kisses, cuddling, etc): Sure! He's a reasonably friendly guy, though he'll feel weird if someone he doesn't know starts getting too close for comfort. He'll start getting skeptical.
Romantic Contact (holding hands, kissing, professions of love, etc): He'll respond better with women, with men, he'll be confused and turn them down.
Sexual Contact: He's a seventeen-year-old boy and has probably kissed and had intimate contact with his girlfriend. I'm a newb with smut myself, but sexual relations with women would more likely fly with good amount of character development. Men? Not so much.
Fighting/Physically Injuring: Sure! He's been trained in Basic at Providence, he'll show your character what he's made of.
Psychological Manipulation: Sure.
Killing: Most likely no
Mind reading/Mind control: Ask me, YMMV

OOC:
Fourth Walling: Generator Rex is an obscure show, and he's in an AU of that, so no.
Threadjacking/hopping: Ask me and others beforehand
Backtagging: Yes.